Dewaxing lubricating oils



settling or centrifuging.

TE orr cs nnwaxmc nunmca'rmc ons Chester a. sum and Frederick w.Sullivan, In.

Hammond, Ind and John A. Anderson, Chialso. 111., assignors to StandardOil Company, Chicago. 111., acorporation or In No Drawing. ApplicationNovember 1. 1933,

Serial No. seams 13 Claims.

This invention relates to the removal oi wax from oils and moreparticularly to the removal of mineral wax from mineral lubricatingoils.

It has been the custom for many years to remove paraiiln wax fromlubricating oil fractions oi petroleum by diluting said fractions with alight petroleum product such as naphtha, chilling the V diluted oil tolow temperatures to precipitate the wax, and removing the wax byfiltering, In this process, a certain amount of wax is dissolved 'in thediluted oil at the dewaxing temperature so that when the diluent isremoved from the oil, said oil has, in general a pour point 16 (asdefined m and determined by Method 1) 91-30 of the American Society forTesting Materials) at least 30* F. and sometimes as much as 50 F.

higher than the temperature ,of dewaxing. It therefore has beennecessary to dewax at extremely low temperatures which necessitatesexpensive refrigeration and which results in decreased flltration ratesbecause of the high viscosity of the diluted oil at the extremely lowtem- 30 whereby extremely low de'waxing temperatures may be avoided.

A further object is to provide an improved diluent mixture and method ofusing the same in a dewaxing process. A further object is to provide aprocess which will dewax oils containing types of wax which wereheretofore 'difllcult or impossible to remove. A further object is to.obtain increased fllter rates and to obtains wax in a more nearlyoil-free condition and in larger yields than 40 has heretofore beenobtained.- Other objects will be apparent from the followingdescription.

lhis problem of providing a satisfactory dewaxing diluent has beendimcult because ordinary diluents dissolve a large amount oi wax, anddiluents 45 which would not dissolve wax would likewise be immisciblewith oil -atdewaxing temperatures. We have discovered that a waxantisolvent may be rendered miscible with a solvent as herein-- afterdefined by means oi certain oxygenated or 5o halogenated compounds whichwe have termed miscibility agents. We have also discovered that certaincracked petroleum products have remarkable new and unexpected propertiesas components in a dewaxing-diluent mixture. Our

.35 invention will be more clearly understood from.

the following description in which examples are described in detail.

To avoid confusion we have defined the meaning of certain terms as theyare used in this speciflcationandinthefoilowing claims.

The term antisolvent refers to a liquid with which wax (and to a lessextent oil) is not miscible in'all proportions at the desired dewaxingtemperature (generally about F. or between liquids are benzol and .moreicularly the cracked petroleum compounds w ch will be hereinafterdescribed and oleflnic hydrocarbons.

The term miscibility agent" may be defined as an oxygenated orchlorinated hydrocarbon completely miscible with the oil at the dewaxingtemperature and capable of preventing the separation of antisolventsfrom oil-diluent mixtures at dewaxing temperatures; among such liquidsare ethyl acetate, ethylene dichloride and iso-propyl ether. 5

The term diluent refers to the whole mixture with which the oil isdiluted and comprises the solvent and antisolvent; 'or solvent,antisolvent and miscibility agent.

When oils are diluted with ordinary diluents and dewaxed, a large amountof wax remains in the solution. In other words, wax is dissolved by thediluent at dewaxing temperatures. It oil is mixed with an antisolventalone, on the other the oil separates from the antisolvent at thetemperatures necessary for complete dewaxing. We have discovered, thatoxygenated and chlorinated hydrocarbons particularly those abovementioned, have the peculiar property of renuent -mixtures used fordewaxing an overhead (distillate) Mid-Continent lubricating oil fractionhaving a viscosity of about 74 seconds Saybolt at21il F. In all of thepreferred embodi-' ments we use two and one-half volumes of diluentmixture to one volume of oil, but it isto'be understood that theseproportions will vary considerably withthe dewaxlng oi' diflerent oilsunder different conditions. From one =volume to four volumes of diluentmixture to one volume of oil hand, dewaxing is practically impossiblebecause are more paramnic than Mid-Continent require greater quantitiesof solvent and less of anti- Solvent. Heavy oils generally require ahigher ratio of solvent to antisolvent in a diluent mixv carbons.

ture than do lighter ones and also require a higher ratio of diluentmixture to oil.

Our preferred solvent is a naphtha or lighter fraction obtained from thereaction products formed by a pyrolytic cracking process, prei'erably avapor phase cracking process wherein gasoil or other petroleum productsare heated to temperatures of about 900-1100 F. under pressures 'of from-300 pounds per square inch.

' This product may be called cracked naphtha to distinguish it from thevirgin or straight run naphtha produced by ordinary distillation. It.

contains a high proportion of olefinic hydrocarbons and it is to thesethat we attribute its outstanding advantages. Naphtha produced by liquidphase cracking is superior as a dewaxing diluent to ordinarynaphtha butit is not as good as that produced by vapor phase cracking. This may bedue to its lower content of olefinic'hydrosince mixtures containinggreater amounts of acetone tend to separate into two liquid bases atdewaxing temperatures. However, the addition of a miscibility agentpermits the use of more acetone and decreases this diflerentlal.

When naphtha produced by liquid phase cracking is used, the maximumacetone content is markedly lower than with a naphtha produced by vaporphase cracking and the resultant oil has an even higher pour point. Anycracked naphtha, however, produces better results than straight runnaphthas and it will thus be seen that cracked naphtha, particularlythose produced by vapor phase cracking are highly desirable constituentsof solvent-antisolvent mixtures whether or not a" miscibility agent isused. In general 15% to 60% of cracked naphtha can be used depending onthe antisolvent used, the nature of the oil being dewaxed, the dewaxingtemperature, the amount of diluent mixture used per-unit of 'oil, andother factors.

We have found that when a miscibility agent is used as a third componentof the diluent mix- I Per cent Iso-propyl ether 15 Acetone 35 Vaporphase cracked naphtha 50 The use of this diluentat a dewaxingtemperamixture.

2,101,187 is, in general, the preferred range. Oilswhichthe threecomponents of high diluent mixture may vary over a considerable range.Compositions which have proved particularly useful are:

Under various conditions the above concentrations of each 01' thesecomponents can be varied as much as 10% or even 15% either up or down.The miscibility agent itself may have a certain antisolvent power butitsparticular usefulness lies in the fact that it has the power to keeplarge amounts of antisolvents from separating from the diluted oil atlow temperatures.

As we have pointed out we believe that thepeculiar advantages oi vaporphase cracked naph thas are due in large part to their high oleflnichydrocarbon content. This is borne out by the fact that olefinichydrocarbons such as propylene, butylene, amylenes, etc., are desirablesolvents and can be used together with antisolvents or antisolvents andmiscibility agents. Thus, for example, from 30% ,to 80% of propylene,butylene, amylene or mixtures thereof can be used together with from to70% of sulfur dioxide as a dewaxing diluent under pressures sufficientto cause liquefaction of the diluent mixture.

While we have disclosed preferred embodiments or our invention in detailit is understood that f we do not limit ourselves to the detailshereinabove set forth except as defined by the following claims whichshould be construed as broadly as the prior art will removing thediluent from the dewaxed oil.

2. The process oi dewaxing a wax-bearing minerallubrica'ting oil whichcomprises diluting the oil with a diluent mixture comprising substantialamounts oi aiwax antisolvent, a cracked petroleum naphtha and amiscibility agent, chilling the diluted oil to a low temperature,whereby the wax is caused to precipitate therefrom while the oil isretained in solution'in the diluent mixture, separating the wax from theoil and diluent, and

subsequently removing the diluent from the dewaxed oil.

3. The process 01' dewaxing mineral lubricating oils according to claim1 wherein the petroleum by a vapor phase cracking naphtha is producedprocess.

4. The-process of dewaxing lubricating mineral oils according to claim 1wherein acetone is em+ ployed as the antisolvent in the diluent mixture.

a v Per cent lsopropyl ether Acetone 33 Vapor phase cracked naphtha 42Percent Ethylene dichloride 43 Acetoneg 16 Cracked naphtha 41 5. Theprocess of: dewaxlng lubricating mineral oils according to claim 2wherein iso-propyl ether is employed as the miscibility agent in thediluent 6. The process 01' dewaxing lubricating mineral oils accordingto claim 2 wherein the diluent mix- 11. The process 0! claim 2 whereinthe antiture employed is comprised of cracked petroleum solvent issulfur dioxide.

naphtha, acetone and iso-propyl ether. 12. The process of claim 2wherein the misci- 7. The process of claim 1 wherein the antibilityagent is ethylene dichloride. I 5 solvent is methyl ethyl ketone. 13.The process of claim 2 wherein the created 5 8. The process oi claim 1wherein the" antipetroleum naphtha is produced by vapor phase solvent issulfur dioxide. cracking.

9. The process of claim 2 wherein the anti- CHESTER E. ADAMS. solvent isacetone. FREDERICK W. SUILIVAEJI.

10 10. The process of claim 2 wherein. the nntl- JOHN A. ANDERSON. l0

solvent is methyl ethyl ketone. l

CERTIFICATE OF CORRECTION. Patent No". 2,107,157. February l, 19 58. 7CHIESI'ER E. ADAMS, ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows Page 2,second column, line 56, claim 2, after "agent" and before the commaInsert the words for antieolvent and oiliahd that the said LettersPatent should be read with this correction therein that the same mayconform tothe record of the ease in the Patent Office.

Signed and sealed this 15th day of March, A. n. 1958.

l I Henry Van Arsdale, (Seal) 7 Acting Commissioner of Patents.

oils according to claim 2 wherein the diluent mix- 11. The process 0!claim 2 wherein the antiture employed is comprised of cracked petroleumsolvent is sulfur dioxide.

naphtha, acetone and iso-propyl ether. 12. The process of claim 2wherein the misci- 7. The process of claim 1 wherein the antibilityagent is ethylene dichloride. I 5 solvent is methyl ethyl ketone. 13.The process of claim 2 wherein the created 5 8. The process oi claim 1wherein the" antipetroleum naphtha is produced by vapor phase solvent issulfur dioxide. cracking.

9. The process of claim 2 wherein the anti- CHESTER E. ADAMS. solvent isacetone. FREDERICK W. SUILIVAEJI.

10 10. The process of claim 2 wherein. the nntl- JOHN A. ANDERSON. l0

solvent is methyl ethyl ketone. l

CERTIFICATE OF CORRECTION. Patent No". 2,107,157. February l, 19 58. 7CHIESI'ER E. ADAMS, ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows Page 2,second column, line 56, claim 2, after "agent" and before the commaInsert the words for antieolvent and oiliahd that the said LettersPatent should be read with this correction therein that the same mayconform tothe record of the ease in the Patent Office.

Signed and sealed this 15th day of March, A. n. 1958.

l I Henry Van Arsdale, (Seal) 7 Acting Commissioner of Patents.

